THE COMING COMET,

Taranaki Daily News, 4 June 1921, Page 9

THE COMING COMET,

AN INTERESING VISITOR. •FRAIL AND HARMLESS.’’ The arrival of the Pons-Winnecke comet, which makes Its periodical approach to the sun every five years or so, is the subject on this occasion of an unusual amount of interest. The reason for this stir which this comparatively small visitor is making is easily told; it is that astronomers have, calculated that it will pass very close to the earth, and the possibility of an actual collision is not excluded. Fortunately, modern knowledge of the na'ture. of comets has abolished all the terrors that even a few years would have attended such a pro&pect. * Even. if a very much, bigger comet should run “slap into” the earth, the consequences, though they might be spectacular, wpqld not be dangerous. At most, it is declared on high authority, there would be a fine, display of meteorites, of which a few scattered stones might reach the earth’s surface. One of the “terrors” that used tq dwell in the minds of comet-fearing people was that the human race' might be asphyxiated by the gases whidh help’ to make up the comet’s extremely tenuous fprm; but this also carries no weight nowadays.

Some interesting- particulars of the Pons-Winnecke visitor are given in the Manchester Guardian by a correspondent who describes it as by no means one of the large ’or important members of the sun’s family of comets.

LOST AND FOUND AGAIN. It was first seen as a faint telescopic object by Pons, of. Marseilles, a famous French astronomer who devoted himself to this branch of astronomy, on 12 ( th. June, 1819. The great German astronomer Encke, whose name is borne by another comet, assigned to this faint object a revolution period of about 51 years. At the end of that period, however, the object was not seen, and it up as lost until on Bt’h March, 1858, it was rediscovered by a German observer, AVinnecke/ at Bonn. For some time Winnecke regarded the comet as a new one, but on calculating its orbit he was' soon led to the conclusion that it was identical with Pons’s lost comet of 1819. Since 1853 the comet has been recognised as a regular member of the sun’s comet family, and has been observed at most of its perihelia, or nearest approaches to the sun.

In 1909 the comet, was due at perihelion. and it was successfully observed by a number of astronomers. It. was found, however, that owing to its near approach to the giant planet Jupiter fts orbit had been considerably altered. By the time of its next return, in 1915-16. a further change had taken place, so that the comet’s orbit now intersected the orbit of the earth. On 28th June, 1916, Mr. W. F. Denning, the greatest living observer of meteors, noticed a shower of meteors which had never been seen before. The meteors, he stated, were "individually not very noteworthy... .fairly bright, slow, objects.” The importance of his observation consisted not in the nature of the meteors themselves, but in the fact that this new shower was observed at a time when, owing to the perturbations produced by Jupiter, the orbit of the PonsWennicke comet intersected that of the earth.

COMETS AND METEORS. The detection of the intimate relation between comets and meteors was one of the greatest discoveries of the nineteenth century. For centuries men of science had regarded meteors, or shoot-ing-stars, as atmospheric phenomena. In 1833, however, a great, shower of meteors took place, and was carefully observed by capable astronomers. It was seen that all the meteors which fell during this shower seemed to come from the same part of the sky. That is to say, their paths when traced backward were found to converge to a point near the star Gamma in the constellation Leo. This observation gave the death-blow to -the view that meteors were of terrestrial origin. Opinion now moved rapidly towards the view that meteors were simply smau particles of matter revolving round the sun in meteoric shower being the result of a collision between the earth and one of these swarms. .

The orbits of several of the bestknown meteor swarms were qpmputed over half a century ago by tame of the foremost mathematicians of the lime, and, to the amazement of the scientific world, Schiaparelli, of Milan, the greatest Italian astronomer of the century, found that the August meteors —the Persaids—moved in an object identical with that of the comet of August, 1862. Later he showed that the orbit of the better-known November meteors —the Leonids—was identical with that of Tempel’s comet of 1866. In a little volume published a few years later Schiaparelli showed conclusively that "meteoric currents are the products of the dissolution of comets, and consist of minute particles which certain comets have abandoned along their orbits by reason of the disintegrating force whiqji the sun and planets exert on the rare materials of which they are composed.” All doubt was removed by what took place in 1872. In November of that year the earth crossed the orbit of the lost comet of Biela, which had not been seen for twenty years and the consequence was one of the most brilliant showers of meteors within human memory.

SHOWER OF METEORS. Mr. Denning announced some time ago that there is a prospect of a brilliant shower of meteors this year on or about the 27th June, when our planet once again crosses the path of the PonsWinneeko comet. There has indeed been considerable discussion as to the possibility of a collision between the earth and the head of the comet. A comet’s head appears to consist simply of loose stones enveloped in gaseous material. Were dur world to strike the comet's head, where the stones are clustered most thickly, the result would be simply a meteoric shower of unusual brilliance. Possibly some of the larger stones might reach the surface of the earth, but the vast majority would be raised to incandescence and reduced to powder as a result of the collision. For comets, which one struck terror into the hearts of men, appear to be of all celestial objects the most frail and harmless.